This invention relates generally to machinist""s tools and more particularly concerns tools for checking the accuracy of machining on a workpiece.
The known method for testing the accuracy of a machined workpiece is to hold a flat surface test tool against the piece to be tested with one hand. A light source is then held on one side of the tool with the other hand and the machinist observes from the other side of the tool whether light appears between the tool and the workpiece. This approach is not very efficient for many reasons.
First of all, without even considering the test procedure itself, it is necessary to have both the tool and the light source close at hand. In reality, they are never where you expect them to be when you need them. They are used for other reasons and not returned to the test area or at least not to the place the machinist would look for them. Some machinists keep a light source with them, but pockets and belts can become quickly cluttered and cumbersome.
Secondly, the light sources themselves are not very efficient. They are, typically, point sources such as a flashlight or the like. A proper test should desirably indicate not only the existence of a flaw on the workpiece surface but the location and severity of the flaw as well. Point sources do not disperse light evenly across the surface to be tested. Therefore, they may not always provide accurate information about the flaw.
Finally, the use of an independent light source with the test tool is at best inefficient and cumbersome and, in some applications, nearly if not entirely impossible. The machinist must deal with at least three objects, the workpiece, the test tool and the light source, with only two hands. The machinist""s eyes must be on one side of the test tool while one hand holds the tool and the other hand holds and properly directs the light source on the opposite side of the tool. This frequently must be accomplished in situations of limited access so that hand positions are dictated or even prohibited by the workpiece. Often, other objects such as surface plates must be simultaneously manipulated.
It is, therefore, an object of this invention to provide a machinist""s accuracy testing tool which has a light source built into the tool. Another object of this invention is to provide a machinist""s accuracy testing tool which disperses light from multiple points along the surface of the workpiece. A further object of this invention is to provide a machinist""s accuracy testing tool which directs the light from a light source to the appropriate workpiece surface. Yet another object of this invention is to provide a machinist""s accuracy testing tool which eliminates the need for holding a light source. It is also an object of this invention to provide a machinist""s accuracy testing tool which makes testing more easy, efficient and accurate. Still another object of this invention is to provide a machinist""s accuracy testing tool which enables testing to be performed in areas of limited space which might otherwise render testing impossible.
In accordance with the invention, a tool for use by a machinist in testing the accuracy of a workpiece is provided. An elongated member has an edge to be abutted against the workpiece to be tested. An encased light source is connected by a plurality of passages extending within the member to the edge. The passages conduct light emitted from the source to an array of apertures spaced at intervals in a bevel of the edge. The array of apertures directs the light at the workpiece on one side of the edge so that defects in accuracy are illuminated to the machinist viewing the workpiece from the other side of the edge. Preferably, the member has a chamber in which the light source is encapsulated. In a specially preferred embodiment, a plurality of fiber optic cords extend in the passages from the light source to the apertures. The tool may be a machinist""s straight edge, a machinist""s square or the like.
For some tools, and especially for squares, it may be desirable to illuminate more than one edge of the tool, such as the inside and outside edges of the square. For such tools, the elongated member has lengthwise opposite first and second edges for abutment with the workpiece to be tested and first and second pluralities of passages extending from the light source to first and second bevels of the first and second edges, respectively. Light is conducted to first and second arrays of apertures spaced at intervals in the first and second bevels, respectively. The first and second arrays of apertures direct the light at the workpiece on one side of their respective edge so that defects in accuracy are illuminated to a machinist viewing the workpiece from the other side of their respective edge. Preferably, the bevels of the first and second edges are on opposite faces of the member so that, for example, a square can be applied at either its outside or inside edges and still be viewed from the same side of the workpiece.
In an alternate embodiment, the edge of the tool may have a cavity extending along its length with an array of apertures spaced along and opening into the cavity. Thus the same edge can be viewed from either side or even both sides simultaneously.